Without limiting the scope of the invention, its background is described in connection with an optical sensor system that may be used to detect the presence of a given sample of interest such as a gas, a liquid or solid.
The use of fluorescence and surface plasmon resonance based technology to detect sample gases and liquids is known by those skilled in the art. A typical application of the fluorescence based sensing involves the molecular labeling of a thin film, cable, or other article, followed by excitation and fluorescent measurement in the presence of the particular sample of interest. Fluorescent labeling involves the deposition of a suitable fluorescent chemistry known to interact with the sample.
A source of excitation light is directed at the coated article, resulting in an emission light. Direct contact with the sample effects changes in the character of the emission light. A spectrograph or other similar instrument can be used to measure the emission thus indicating the presence and concentration thereof.
In surface plasmon resonance based sensing, a source of electromagnetic radiation (light) strikes a thin conducting layer and is partially reflected toward an array of radiation detectors. The light internally reflected by the conducting layer has a minimum intensity at a particular angle referred to as the resonance angle. Therefore, the radiation detector having the minimum output level is associated with the light rays that have reflected off the conducting layer at the resonance angle, which is a function of the refractive index of the ambient sample. By detecting the angle at which resonance occurs, the refractive index may be determined and used to identify the sample.
One limitation of the prior art sensor systems is that they are not fully integrated; most are interfaced with equipment such as a personal computer or hand held instrument to perform measurement and analysis. Furthermore, chemical sensing by optical means often requires the exposure of a sensor surface to the ambient under test. While the electro-optic components may be protected, the connector pins remain exposed. In many applications, however, protecting the electro-optic components and electrical connections is critical such as in liquid-based applications which may require submersion of the sensor into the sample.
Also, the separate and additional circuitry used to interface the prior art sensors to remote processing systems increases total system cost and maintenance.
What is needed is a sensor system that integrates the electro-optic components in a self-contained package. A system that permits the wireless transfer of data to a personal computer or other processing platform would have great advantages over the prior art systems. The present invention solves the aforementioned problems by incorporating the necessary system elements within a self-contained sensor package.